采用第一原理赝势平面波方法计算了Al-Sc合金固溶体、有序相和无序相结构对应的形成焓. 在无序合金的电子结构研究中, 引入了可以描述无序合金结构环境的小尺寸超单胞模型-SQS模型. 计算结果表明: 超饱和固溶体中的Sc原子具有偏聚产生L12结构的Al3Sc析出相和L10结构的AlSc析出相的趋势. 依据对各相的电子结构及电子密度分析结果, 初步探讨了时效处理导致超饱和固溶体Al(Sc)中偏聚产生L12结构Al3Sc析出相的形成机理.
The formation enthalpies of the Al-Sc compounds and the Al-rich solid solution phase have been studied from first-principles based on plane--wave pseudopotential method. To calculate the electronic structure of the disordered Al-Sc alloys, the small-size special quasirandom structures (SQS), which exhibited similar structure environments as that of the disordered Al-Sc alloys, are employed. It is shown that the Sc atoms in supersaturated solid solution tend to segregation forming ordered Al3Sc< (L12) and AlSc (L10) precipitations. The nucleation mechanism of Al3Sc precipitation phase in the supersaturated Al(Sc) solid solution is analyzed in terms of the calculated densities of states and distributions of electron densities.
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